1. Field of the Invention
This invention generally relates to an auger type ice making machine in which ice layers formed on the inner cylindrical surface of a refrigeration casing are scraped off as a rotary screw shaft with a coiled blade rotated in the casing. More particularly, the invention is concerned with a rotary cutter device mounted on the top of the screw shaft extending upwardly through an extrusion head, which is secured to the upper end portion of the refrigeration casing, for cutting ice rods extruded through the extrusion head into small particles of ice, known commercially as ice chips or pellets.
2. Prior Art
In the ice making machine of the auger type mentioned above, thin ice layers formed on the inner cylindrical surface of the refrigeration casing are scraped therefrom by the coiled blade of a screw shaft rotatably supported by bearings at upper and lower ends thereof and form a semi-solid frozen material. The semi-solid ice mass is fed upwardly through a plurality of ice compressing passages in the extrusion head to be extruded in the form of ice rods from the extrusion head which is securely mounted within the casing, the ice rods then cut into hard ice particles, i.e. ice pellets or chips by a cutter mounted on the screw shaft at the top end thereof. A variety of such ice making machines are known (reference may be made to U.S. Pat. No. 4,484,455, for example).
Further, it is already known that the discharge of the ice chips or pellets resulting from the cutting by the cutter in the ice making machine can be promoted or accelerated by using a cutter having a plurality of radially outwardly extendng, circumferentially spaced fin-like cutter blades (reference may be to Japanese Utility Model Publication No. 61-32306, for example).
When it is desired to obtain fine ice particles by cutting the ice rods with the fin-like cutter blades, a cutter device is employed wherein the cutter blades thereof are circumferentially arranged at a smaller pitch instead of lowering the ice extruding speed by decreasing the rotating speed of the screw shaft, as a reduction in ice extruding speed is unfavorable to ice manufacturing efficiency.
However, when the circumferential pitch of the cutter blades is small, i.e. when the inter-blade space is narrow, the inter-blade spaces become jammed or crammed with fine ice particles, which are then compressed therein to be excessively hardened beyond a desired hardness and may eventually grow to harder particulate ice of a larger size.
Also, conventional auger type ice making machines suffer from other shortcomings. More specifically, referring to FIG. 4 of the accompanying drawings, the ice layers formed on the inner surface of a refrigeration casing (not shown) are scraped off and compressed into ice rods through an extrusion head (not shown), wherein the ice rods are cut by cutter blades 17 of a rotating cutter 13 into ice particles, which are then introduced from a discharge port 22 connected to the casing and through a not shown ice discharge chute into an ice storage bin (not shown). When the discharge port 22 is formed of, for example, a plastic material, harder ice mass in larger particulate form tends to jam in a gap 22a between the discharge port wall and the radially outermost ends of the cutter blades 17 to thereby injure or break the discharge port 22 and/or apply an increased load onto the bearings of the screw shaft 2 by way of the cutter blade edge, cutter 13 and screw shaft 2, exerting various adverse influences on the ice making machine, including accelerated abrasion of the bearings and other parts.